1. Field of the Invention
The present invention relates to a nonaqueous electrolytic secondary battery comprising a positive electrode active material capable of intercalating and deintercalating a lithium ion, a negative electrode active material capable of intercalating and deintercalating the lithium ion, and a nonaqueous electrolyte, and a method of manufacturing the nonaqueous electrolytic secondary battery.
2. Description of the Related Art
For a battery to be used in portable electronic and communicating equipment such as a small-sized video camera, a mobile telephone and a notebook personal computer, recently, a nonaqueous electrolytic secondary battery having an alloy or a carbon material capable of intercalating and deintercalating a lithium ion as a negative electrode active material and lithium containing transition metal oxide, for example, lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2) or lithium manganese oxide (LiMn2O4) as a positive electrode active material has been put into practical use to be a battery having a small size, a light weight and a high capacity and capable of carrying out a charge and discharge.
Since lithium nickel oxide (LiNiO2) in the lithium containing transition metal oxide to be used for the positive electrode active material of the nonaqueous electrolytic secondary battery has a feature of a high capacity and a drawback of a poor safety and a high overvoltage, it is inferior to the lithium cobalt oxide. Moreover, lithium manganese oxide (LiMn2O4) has a rich source and is inexpensive, and has a drawback; that an energy density is low and manganese itself is dissolved at a high temperature. Therefore, it is inferior to the lithium cobalt oxide. At the present time, accordingly, the use of the lithium cobalt oxide (LiCoO2) to be the lithium containing transition metal oxide has been a mainstream.
However, it has been known that the lithium cobalt oxide is deteriorated by a charge and discharge. The degree of the deterioration is correlated with the crystallinity of the lithium cobalt oxide and is remarkable with a low crystallinity of the lithium cobalt oxide. Furthermore, if the crystallinity of the lithium cobalt oxide is low, lithium is removed from the lithium cobalt oxide during charging so that an unstable state is set and oxygen is apt to be desorbed from the lithium cobalt oxide. For this reason, there is a problem in that the lithium cobalt oxide having a low crystallinity is not sufficient in respect of a thermal stability, resulting in a poor safety.